What caused last summer's massive floods? Probe of regional water authority released

A heavy, historic rainstorm was primarily to blame for last summer's devastating floods in metro Detroit, although damage was "likely exacerbated" by electrical problems at two east-side pumping stations that reduced the ability to pump wastewater by more than a quarter, a panel of experts reported Wednesday.

Investigators used data and technical models to project what would have happened if the system managed by Great Lakes Water Authority (GLWA) worked "as intended" without electrical issues on June 25-26, 2021, when 6 to 8 inches of rain fell over a 24-hour period across the area.

What they found was the Conner Creek and Freud pumping stations could have handled another 26% of the flow — or 336 million gallons — if all seven stormwater pumps were working at both stations. Freud had only three pumps running because of a damaged power line and Conner Creek had just five pumps working shortly before 2 a.m., after a power issue delayed three pumps from starting.

But even if all pumps were working fully, widespread basement backups and surface flooding in roadways was "inevitable," according to investigators who reported their findings at a GLWA Board of Directors meeting Wednesday.

“The intensity of the rainfall far exceeded the designed capacity of the wastewater system and, as a result, some level of both surface flooding and basement backups was unavoidable,” the report reads.

"An analysis of risk of basement backups did not show an appreciable reduction in risk if everything had worked as intended.”

Read the report online here.

It's not clear from the report how much experts believe the pumping problems could have worsened basement flooding. But GLWA officials said Wednesday that it could have meant additional inches of water in an already flooded basement.

The investigation's release comes just days before the one-year anniversary of the June 25-26 flood that  resulted in a four-county federal disaster declaration, more than 67,000 damage claims filed with the Federal Emergency Management Agency (FEMA) and about a dozen lawsuits against GLWA and others. The brunt of the storm hit Detroit, Dearborn, Garden City, Ypsilanti and the Grosse Pointes.

The rainfall qualified as historic: between a 200-year to 1,000-year storm depending on the area where rain fell, according to investigators. GLWA’s system is designed for a 10-year storm of 1.7 inches of rain falling over an hour or 3.31 inches in 24 hours.

The experts who presented Wednesday were hired directly by GLWA board members, who said last summer they wanted an independent investigation into the problems and appointed Jeffrey Collins, an attorney, former judge and former U.S. attorney, to run the probe. The principal investigator for the report was University of Michigan professor  Glen Daigger, who was assisted by AECOM Technical Services.

Among other findings from the report:

• Surface flooding on streets and roadways could have been reduced if the pumping stations would have operated properly in June. "The areas that experienced surface flooding greater than two feet could have been reduced by approximately 110 acres," the report stated.

• Grosse Pointe Park and the city of Grosse Pointe "significantly exceeded" the limits on how much wastewater they were pumping into GLWA facilities during the June storm, but according to the analysis the levels "did not significantly affect basement backup flooding" in other areas. There are no financial penalties for exceeding limits, GLWA said. Officials from both cities said they hadn't seen the report yet.  "As such, I can only assume the report it what we suspected all along — that the report is a way to try to divert attention from GLWA's responsibility for the obvious breakdowns of their system that had disastrous results for everyone on the east side," Grosse Pointe City Manager Peter Dame wrote in an email.

• Flooding on the city's west side and in suburbs like Dearborn was extensive, but GLWA has said there weren't the same problems as on the east side with its facilities. But investigators said the Baby Creek Enclosure Sewer on the west side had reduced capacity because of sludge buildup, and that could have raised wastewater levels upstream. That sewer district covers the north central part of Detroit, most of Highland Park and a small portion of southeast Dearborn.

• A lock on a pedestrian gate at Conner Creek had to be cut open so a GLWA electrician could get in to work on repairs because the vehicle gate wouldn't open when the house power went out.

• The investigation also delves into the July 16 flooding. It wasn't as extensive as the June backups, but still damaged hundreds of properties primarily in Detroit, Dearborn and eastern suburbs. Electrical problems at the Bluehill Pump Station on the city's east side was also a factor in the July flooding, but it's "not known whether local basement flooding complaints could have been reduced if the system (had) operated as intended," the report said.

Attorney David Dubin represents clients with nearly 3,000 homes and businesses suing over their flood damage and said that despite the findings, he is convinced the GLWA pump breakdowns significantly contributed to the flooding.

“They heard what they wanted to hear and that is, ‘We aren’t at fault,’” Dubin said. “There needs to be a truly independent investigation through the court system.

“I’ve had thousands of clients who have suffered hundreds of millions of dollars who are still dealing with the trauma of this event who are picking through their lives and trying to put their homes back together.”

GLWA faced heavy scrutiny on the role human error played in the weeks after the June backups, in part because repeated flooding has plagued residents in cities across the region in recent years. GLWA officials have consistently said that an intense amount of rain primarily caused the June flooding but acknowledged electrical problems.

Employees were aware of the power outage at Freud three days before the June storm. But the former CEO, Sue McCormick, had said she only knew of the electrical problem the morning of the storm.

McCormick resigned in July. Interim CEO Suzanne Coffey was offered the CEO position on Wednesday after a national search.

No GLWA staff members have been reprimanded for actions related to the June flooding because policies were followed, Coffey said Wednesday. After the June flood, procedures were changed to require that  upper management be notified of similar problems.

GLWA staff also hired its own investigators to examine the flood. Both sets of investigators came to "essentially the same" conclusions that the heavy rain was to blame, so the board asked both groups to work together, according to the final report that was issued Wednesday.

Combined, both investigations are expected to cost $2.75 million.

The report also made a series of short- and long-term recommendations, including starting up generators during anticipated heavy rains so they are ready to go if needed, making improvements to the complicated vacuum priming system at Conner Creek and even buying out homeowners in flood-prone areas.

GLWA officials say they've taken steps to reduce future floods, ranging from installing three new transformers at Freud and converting its power supply to three independent DTE Energy feeds, installing devices to give advance notice of power outages and establishing better communication with east and west side communities.

But Coffey acknowledged a similar sized storm would cause the same flooding today. She said GLWA is working to find funding for a Flood Risk Mitigation Study for southeast Michigan that would identify long-term steps, such as deep tunnel systems that could relieve pressure on the system.

"We are seeing that climate change is on us more rapidly than we had intended and more intensely," Coffey said. "So now is the moment for this type of thing, especially because there's a huge focus on infrastructure right now."

More than 40,000 separate damage claims from the flooding have been filed with the Detroit Water and Sewerage Department or GLWA.

DWSD has already predicted most claims will be denied. Under Michigan law, the city or GLWA can be held responsible only if there was a defect — one it knew about or should have known about — that it didn't fix and was 50% or more at fault for the flooding.

GLWA officials on Wednesday wouldn't comment on the likelihood of claims being denied. They expect decisions on the claims by mid-July.

READ MORE: Investigators pushed for basement flooding text alerts. But Detroiters never got them.

READ MORE: Thousands of Detroit flood victims still waiting for aid 9 months later

Contact Christine MacDonald: cmacdonald@freepress.com or 313-418-2149.

This article originally appeared on Detroit Free Press: Probe into last summer's floods blames rain but power issues contributed